Mechanisms of 1s Double-Core-Hole Excitation and Decay in Neon

Maksim D Kiselev,Sergei M Burkov,Alexei N Grum-Grzhimailo,Elena V Gryzlova,Oleg Zatsarinny

doi:10.3390/atoms9040114

Maksim D Kiselev, Sergei M Burkov + Show 3 more

Open Access

https://doi.org/10.3390/atoms9040114

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Abstract

The formation and decay of double-core-hole (DCH) states of the neon ion irradiated by an intense electromagnetic x-ray field are studied theoretically. In the present research DCH formation is the result of sequential absorption of two photons with the creation of an intermediate ion. Detailed calculations of the partial decays and probabilities of shake-ups at the atomic and ionic ionization stages are presented. The angular distribution of photoelectrons corresponding to various residual ionic states are calculated. Specifically, we predict the lack of any photoelectrons corresponding to the residual ionic state 1s12s22pnmpn′2Sf+1D in the direction of the electric field polarization. Dynamical competition between single-core-hole state decay and excitation is analyzed and pulse parameters corresponding to various dynamical regimes are found.

Highlights

Investigations of formation and decay double-core-hole states (DCH) are of great importance for both fundamental physics and applications such as radioactive damage of biological samples for coherent diffraction imaging [1,2,3]
With the advent of Free-Electron Lasers (FELs), these states became available in the nonlinear sequential ionization regime when there is a time delay δt between the formation of single and double core-hole states, and there is a dynamical competition between the Auger decay of single-core-hole states (SCH) and excitation to double-core-hole states [14,15,16]
In the present research we expect that sequential mechanism is dominant due to resonant enhancement, that confirms by experimental observation in [16]

Summary

Introduction

Investigations of formation and decay double-core-hole states (DCH) are of great importance for both fundamental physics and applications such as radioactive damage of biological samples for coherent diffraction imaging [1,2,3] They are crucial for molecular spectroscopy because of the large chemical shifts in DCH states. (a) If the photon energy is below the Ne+ 1s-shell ionization threshold, either Auger decay to a Ne2+ state occurs or resonant excitation of 1s to an np state. The latter process becomes dominant with increasing pulse intensity. The excited states may decay to a variety of Ne2+ states via processes including: Auger, two-to-one shake-up, conjugate shake-up, etc. (b) If the photon energy is above the Ne+ 1s-shell ionization threshold, the Auger decay of 1s12s22p6 2S competes with ionization to Ne2+ with subsequent decay to Ne3+

Models and the Photoabsorption Spectrum

Photoelectron Spectrum and Angular Distribution

Population of Atomic and Ionic States in Multiple Ionization

Findings

Conclusions